It is a long answer, but I'll try
Prior to the industrial revolution, wealth was measured in how much land you had since things were still agriculturally based. Because of the industrial revolution and we started making things, we therefore had to start
buying things, and the measure of wealth moved to material possessions and money.
Now, you had all these sons of nobles set to inherit all this land but land didn't mean shyt anymore. So they decided to make a name for themselves in other ways and being an explorer was one of them. David Livingston ("founder" of the Victoria falls) and Cecil Rhodes ( name sake of the country formerly known as Rhodesia) were the son of rich nobles.
Because these explorers claimed the land of the country they were from, all of that African countries resources were now the property of the European country, so they got rich and other countries wanted to get some of the action and started sending folks down their to claim land.
It also didn't hurt that the euros thought the Africans were "godless heathens and savages" so they kinda felt justified in being down there too, to I guess save their souls.
You're welcome